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Index › Programming Questions & Help › Syntax Questions › two floats input, one float output
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two floats input, one float output (Read 1042 times)
aletropdj0
two floats input, one float output
Feb 12th, 2010, 9:44am  
hi all.

there is some way to with the mouseX and mouseY, give me only one float?

I tryed with atan2, but the output give me stange numbers(f.ex: 0.001;0.41616, 1.6542)...i need to transform this numbers in real numbers depending on the size of the window.

any idea?

thanks
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TfGuy44
Re: two floats input, one float output
Reply #1 - Feb 12th, 2010, 10:14am  
First of all, mouseX and mouseY are ints, not floats.

I suspect what you want is
int result = mouseX + ( width * mouseY );

If not, post your code for what you're trying to do.
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Cedric
Re: two floats input, one float output
Reply #2 - Feb 12th, 2010, 10:15am  
what should that one float be ?
i mean mouseX and Y are coordinates. but what do you want ? the distance from 0,0 ? the agle ?
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Bloom
Re: two floats input, one float output
Reply #3 - Feb 12th, 2010, 11:14am  
yeah, Cedric's right,
if your in two dimensions, you need two values, three dim... 3 values.
there is no relation between x value and y value... these are independant.
Thats the same for the arrays...
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Quark
Re: two floats input, one float output
Reply #4 - Feb 12th, 2010, 12:20pm  
Quote:
there is some way to with the mouseX and mouseY, give me only one float?


As the others have said, explain why you want one float and it might give us a clue on how to answer.  Roll Eyes

Anyway the following will calculate the angle (in degrees expressed as a float) of the line from the top left corner of the window to the current mouse position relative to the horizontal.

Code:
degrees(atan2(mouseY, mouseX));


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aletropdj0
Re: two floats input, one float output
Reply #5 - Feb 13th, 2010, 6:53am  
Cedric wrote on Feb 12th, 2010, 10:15am:
what should that one float be
i mean mouseX and Y are coordinates. but what do you want the distance from 0,0 the agle


ya cedric!

i want the distance from 0,0(origin)! i think atan2 gives me the angle, but i want the distance
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Quark
Re: two floats input, one float output
Reply #6 - Feb 13th, 2010, 7:21am  
The distance of the mouse from the origin (i.e. top left corner is given by

Code:
sqrt(mouseX*mouseX + mouseY * mouseY)


Smiley
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TfGuy44
Re: two floats input, one float output
Reply #7 - Feb 13th, 2010, 8:14am  
Or
dist(0, 0, mouseX, mouseY);
Grin
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blindfish
Re: two floats input, one float output
Reply #8 - Feb 13th, 2010, 8:26am  
TfGuy44 wrote on Feb 13th, 2010, 8:14am:
Or
dist(0, 0, mouseX, mouseY);
Grin


dist() is convenient but I can't imagine it's any quicker than Quark's suggestion (which is also a handy reminder that the calculation of distance is simply an application of pythagorus's theorum).  Also if you're using this for collision detection (i.e you don't need to report the actual distance, just act upon it) then using the longhand method suggests a commonly used optimisation for collision detection:

Code:
int distSquared = mouseX*mouseX + mouseY*mouseY;
int thresholdDistanceSquared = thresholdDistance*thresholdDistance;

if(distSquared < thresholdDistanceSquared) {
  // collision...
}


sqrt() is apparently slower in comparison to adding the extra multiplication (which itself isn't necessary if the value can be hard-coded; though avoid magic-numbers)...
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Where is the what if the what is in why?
 
TfGuy44
Re: two floats input, one float output
Reply #9 - Feb 13th, 2010, 8:34am  
Well yeah. I was just suggesting to use dist() because when I see:

"dist( 0, 0, mouseX, mouseY );"

I think:

Smiley Ah! This gets the distance between (0,0) and the mouse's position! Cool

But when I see:

"sqrt( mouseX * mouseX + mouseY * mouseY );"

I think:

Shocked Huh? What does that lin- Oh, it gets the distance between (0,0) and the mouse's position. Right. Why didn't I just write "dist( 0, 0, mouseX, mouseY );"? Huh
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aletropdj0
Re: two floats input, one float output
Reply #10 - Feb 15th, 2010, 8:55am  
thanks all.

dist() resolv my problem.

always learning
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